For the purposes of this research, air treatment systems (also known as air purifiers) are portable systems and are defined as the following:
- Ultraviolet (UV) AirPurifiers
- IonGenerators/Ionizers
- OzoneGenerators
- Electrostatic Air Purifiers, Charged MediaFilters
- Hybrid/Combined AirPurifiers
- HEPA (High Efficiency Particulate Air)Filters
- Activated CarbonSystems
- Photo Catalytic Oxidation AirPurifiers
- Others (any othertechnology)
